Actuator, optical scanner, and image forming device

ABSTRACT

An actuator includes: a first oscillatory system including a frame-shaped driving member and a pair of first axial members holding the driving member from both ends so as to allow the driving member to rotate around an X-axis; a second oscillatory system including a movable plate provided inside the driving member and a pair of second axial members holding the movable plate to the driving member from both ends so as to allow the movable plate to rotate around a Y-axis perpendicular to the X axis; and a driving unit including a permanent magnet provided on the driving member, a coil provided so as to face the permanent magnet, and a voltage applying unit applying a voltage to the coil. The permanent magnet is provided such that a line segment connecting both poles is slanted with respect to each of the X-axis and the Y-axis, in a plan view of the movable plate. The voltage applying unit includes a voltage generating section that generates a first alternating voltage and a second alternating voltage each of which having a frequency different from each other, and a voltage superimposing section that superimposes the first voltage and the second voltage, and the movable plate is rotated around the Y-axis at a frequency of the second voltage while being rotated around the X axis at a frequency of the first voltage by applying the voltage superimposed by the voltage superimposing section to the coil.

BACKGROUND

1. Technical Field

The present invention relates to an actuator, an optical scanner, and animage forming device.

2. Related Art

An optical scanner is disclosed that scans light two dimensionally anddraws images by scanning light in a printer or the like. For example,refer to JP-A-8-322227.

The optical scanner disclosed in JP-A-8-322227 includes a scanner mainbody including a frame-shaped outer movable plate, a pair of firsttorsion bars axially supporting the outer movable plate so as to allowthe outer movable plate to swing (rotate) around an X-axis, an innermovable plate provided inside the outer movable plate, and a pair ofsecond torsion bars axially supporting the inner movable plate to allowthe inner movable plate to swing around a Y-axis perpendicular to theX-axis. The optical scanner also includes a pair of driving coilsrespectively provided on the outer movable plate and the inner movableplate, and a pair of permanent magnets provided so as to face each otherwith the scanner main body therebetween.

However, in such optical scanner, the pair of permanent magnets isprovided so as to face each other with the scanner main bodytherebetween. Therefore, it is difficult to downsize the opticalscanner. In addition, it is also difficult to reduce the costs since thedriving coil is respectively provided on the outer movable plate and theinner movable plate.

SUMMARY

An advantage of the present invention is to provide an actuator in whicha movable plate can be rotated around each of an X-axis and a Y-axis, anoptical scanner, and an image forming device while achieving low costsand downsizing.

The above advantage is achieved as follows.

An actuator of a first aspect of the invention includes a firstoscillatory system, a second oscillatory system, and a driving unit. Thefirst oscillatory system includes a frame-shaped driving member and apair of first axial members. The pair of first axial members holds thedriving member from both ends so as to allow the driving member torotate around an X-axis. The second oscillatory system includes amovable plate provided inside the driving member and a pair of secondaxial members. The pair of second axial members holds the movable plateto the driving member from both ends so as to allow the movable plate torotate around a Y-axis perpendicular to the X-axis. The driving unitincludes a permanent magnet provided on the driving member, a coilprovided so as to face the permanent magnet, and a voltage applying unitthat applies a voltage to the coil. The permanent magnet is providedsuch that a line segment connecting both poles is slanted with respectto each of the X-axis and the Y-axis, in a plan view of the movableplate. The voltage applying unit includes a voltage generating sectionand a voltage superimposing section. The voltage generating sectiongenerates a first alternating voltage and a second alternating voltageeach of which having a frequency different from each other. The voltagesuperimposing section superimposes the first voltage and the secondvoltage. The movable plate is rotated around the Y-axis at a frequencyof the second voltage while being rotated around the X-axis at afrequency of the first voltage by applying the voltage superimposed bythe voltage superimposing section to the coil.

As a result, an actuator can be provided in which the movable plate canbe rotated around each of the X-axis and the Y-axis, while achieving lowcosts and downsizing.

In the actuator, it is preferable that the frequency of the firstvoltage be equal to a resonance frequency of the first oscillatorysystem or the frequency of the second voltage be equal to a resonancefrequency of the second oscillatory system.

As a result, the movable plate can be smoothly rotated around each ofthe X-axis and the Y-axis.

In the actuator, it is preferable that the frequency of the secondvoltage be equal to the resonance frequency of the second oscillatorysystem and the frequency of the first voltage differ from the resonancefrequency of the first oscillatory system.

As a result, the movable plate can be very smoothly rotated around eachof the X-axis and the Y-axis.

In the actuator, it is preferable that the frequency of the secondvoltage be higher than the frequency of the first voltage.

As a result, the movable plate can be reliably and smoothly rotatedaround the Y-axis at the frequency of the second voltage, while beingrotated around the X-axis at the frequency of the first voltage.

In the actuator, it is preferable that the permanent magnet have alongitudinal shape and be provided along a line segment that passesthrough an intersection of the X-axis and the Y-axis and slants at anangle of from 30 to 60 degrees with respect to the X-axis or the Y-axis.

As a result, the movable plate can be very smoothly rotated around eachof the X-axis and the Y-axis.

In the actuator, it is preferable that the permanent magnet have arelief section to avoid making contact with the movable plate.

As a result, the movable plate can be more smoothly rotated around theY-axis.

In the actuator, it is preferable that the relief section be a recessformed on a surface of the permanent magnet, the surface being at a sideadjacent to the movable plate.

As a result, the relief section can be very easily formed.

In the actuator, it is preferable that the coil be provided directlybelow the permanent magnet.

As a result, the power consumption reduction and size reduction of theactuator can be achieved.

In the actuator, it is preferable that the coil be formed so as tosurround an outer circumference of the driving member, in the plan viewof the movable plate.

As a result, the separating distance between the coil and the permanentmagnet can be shortened greatly. Therefore, a magnetic field generatedfrom the coil can efficiently work on the permanent magnet.

In the actuator, it is preferable that the movable plate include a lightreflecting section having a light reflective characteristic on onesurface opposing the other surface facing the permanent magnet.

As a result, the actuator can be used as an optical device included inimage forming devices such as laser printers, bar code readers, confocalscanning laser microscopes, and imaging displays.

An optical scanner according to a second aspect of the inventionincludes a first oscillatory system, a second oscillatory system, and adriving unit. The first oscillatory system includes a frame-shapeddriving member and a pair of first axial members. The pair of firstaxial members holds the driving member from both ends so as to allow thedriving member to rotate around an X-axis. The second oscillatory systemincludes a movable plate provided inside the driving member, and a pairof second axial members. The movable plate includes a light reflectingsection having a light reflective characteristic. The pair of secondaxial members holds the movable plate to the driving member from bothends so as to allow the movable plate to rotate around a Y-axisperpendicular to the X-axis. The driving unit includes a permanentmagnet provided on the driving member, a coil provided so as to face thepermanent magnet, and a voltage applying unit that applies a voltage tothe coil. The permanent magnet is provided such that a line segmentconnecting both poles is slanted with respect to each of the X-axis andthe Y-axis, in a plan view of the movable plate. The voltage applyingunit includes a voltage generating section and a voltage superimposingsection. The voltage generating section generates a first alternatingvoltage and a second alternating voltage each of which having afrequency different from each other. The voltage superimposing sectionsuperimposes the first voltage and the second voltage. The movable plateis rotated around the Y-axis at a frequency of the second voltage whilebeing rotated around the X-axis at a frequency of the first voltage byapplying the voltage superimposed by the voltage superimposing sectionto the coil. Light reflected by the light reflecting section istwo-dimensionally scanned.

As a result, an optical scanner can be provided that can rotate movableplate around each of the X-axis and the Y-axis and two-dimensionallyscan light, while achieving low costs and downsizing.

An image forming device according to a third aspect of the inventionincludes an optical scanner that includes a first oscillatory system, asecond oscillatory system, and a driving unit. The first oscillatorysystem includes a frame-shaped driving member and a pair of first axialmembers. The pair of first axial members holds the driving member fromboth ends so as to allow the driving member to rotate around an X-axis.The second oscillatory system includes a movable plate provided insidethe driving member and a pair of second axial members. The movable platehas a light reflecting section having a light reflective characteristic.The pair of second axial members holds the movable plate to the drivingmember from both ends so as to allow the movable plate to rotate arounda Y-axis perpendicular to the X-axis. The driving unit includes apermanent magnet provided on the driving member, a coil provided so asto face the permanent magnet, and a voltage applying unit that applies avoltage to the coil. The permanent magnet is provided such that a linesegment connecting both poles is slanted with respect to each of theX-axis and the Y-axis, in a plan view of the movable plate. The voltageapplying unit includes a voltage generating section and a voltagesuperimposing section. The voltage generating section generates a firstalternating voltage and a second alternating voltage each of whichhaving a frequency different from each other. The voltage superimposingsection superimposes the first voltage and the second voltage. Themovable plate is rotated around the Y-axis at a frequency of the secondvoltage while being rotated around the X-axis at a frequency of thefirst voltage by applying the voltage superimposed by the voltagesuperimposing section to the coil. Light reflected by the lightreflecting section is two-dimensionally scanned.

As a result, an image forming device can be provided that includes theoptical scanner that can rotate movable plate around each of the X-axisand the Y-axis and two-dimensionally scan light, while achieving lowcosts and downsizing.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a perspective view of an actuator according to an exemplaryembodiment of the present invention.

FIG. 2 is a sectional view taken along line A-A in FIG. 1.

FIG. 3 is a block diagram of a voltage applying unit of a driving unitincluded in the actuator shown in FIG. 1.

FIGS. 4A and 4B are diagrams showing an example of voltages generated ata first voltage generating section and a second voltage generatingsection shown in FIG. 3.

FIG. 5 is a schematic view illustrating an image forming device of theinvention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

An actuator, an optical scanner, and an image forming device accordingto an exemplary embodiment of the invention will be described withreference to the accompanying drawings.

FIG. 1 is a plan view of the actuator according to the exemplaryembodiment of the present invention. FIG. 2 is a sectional view takenalong line A-A in FIG. 1. FIG. 3 is a block diagram of a driving unitincluded in the actuator shown in FIG. 1. FIGS. 4A and 4B are diagramsshowing an example of voltages generated at a first voltage generatingsection and a second voltage generating section shown in FIG. 3. Forexpository convenience, the front side, the rear side, the right side,and the left side in FIG. 1 are described as “up,” “down or low,”“right,” and “left” respectively. Likewise, the top side, the bottomside, the right side, and the left side in FIG. 2 and FIG. 3 aredescribed as “up,” “down or low,” “right,” and “left” respectively.

As shown in FIG. 1, an actuator 1 includes a substrate 2 that includes afirst oscillatory system 21 and a second oscillatory system 22. As shownin FIG. 2, the actuator 1 also includes a supporting substrate 3, acounter substrate 5, and a driving unit 6. The supporting substrate 3supports the substrate 2 with a bonding layer 4 therebetween. Thecounter substrate 5 faces the substrate 2 with the supporting substrate3 therebetween. The driving unit 6 respectively drives the firstoscillatory system 21 and the second oscillatory system 22.

As shown in FIG. 1, the substrate 2 includes a frame-shaped supportingsection 23, the first oscillatory system 21 supported by the supportingsection 23, and the second oscillatory system 22 supported by the firstoscillatory system 21.

The first oscillatory system 21 includes a frame-shaped driving member211 and a pair of first axial members 212 and 213. The driving member211 is provided inside the supporting section 23. The pair of firstaxial members 212 and 213 holds the driving member 211 to the supportingsection 23 from both ends. The second oscillatory system 22 includes amovable plate 221 and a pair of second axial members 222 and 223. Themovable plate 221 is provided inside the driving member 211. The pair ofsecond axial members 222 and 223 holds the movable plate 221 to thedriving member 211 from both ends.

In other words, the substrate 2 includes the movable plate 221, the pairof second axial members 222 and 223, the driving member 211, the pair offirst axial members 212 and 213, and the supporting section 23.

The driving member 211 is disk-shaped in plan view of FIG. 1 (in otherwords, in a plan view of the movable plate 221). However, the shape ofthe driving member 211 is not particularly limited as long as thedriving member 211 is in the shape of a frame. A permanent magnet 61,described hereafter, is provided on a bottom surface of the drivingmember 211. The driving member 211 is supported and held to thesupporting section 23 from both ends by the pair of first axial members212 and 213.

Each of the first axial members 212 and 213 is longitudinally shaped andcan be elastically deformed. Each of the first axial members 212 and 213connects the driving member 211 and the supporting section 23 so as toallow the driving member 211 to rotate relative to the supportingsection 23. The first axial members 212 and 213 are coaxially provided.The driving member 211 rotates relative to the supporting section 23with the coaxial axis (referred to, hereinafter, as a “rotation centeraxis X”) as the center.

The movable plate 221 formed inside the driving member 211 has acircular shape in the plan view. However, the shape of the movable plate221 is not limited. A light reflecting section 221 a having alight-reflective characteristic is formed on the top surface of themovable plate 221. The movable plate 221 is held to the driving member21 from both ends by the pair of second axial members 222 and 223.

Each of the second axial members 222 and 223 is longitudinally shapedand can be elastically deformed. Each of the second axial members 222and 223 connects the movable plate 221 and the driving member 211 so asto allow the movable plate 221 to rotate relative to the driving member211. The second axial members 222 and 223 are coaxially provided. Themovable plate 221 rotates relative to the driving member 211 with thecoaxial axis (referred to, hereinafter, as a “rotation center axis Y”)as the center.

As shown in FIG. 1, the rotation center axis X and the rotation centeraxis Y are perpendicular to each other. In other words, the rotationcenter axis X and the rotation center axis Y form a 90-degree angle.Each of the center of the driving member 211 and the center of themovable plate 221 is positioned on the intersection of the rotationcenter axis X and the rotation center axis Y in plan view of FIG. 1.

The substrate 2 is mainly made of, for example, silicon. The movableplate 221, the second axial members 222 and 223, the driving member 211,the first axial members 212 and 213, and the supporting section 23 areformed integrally. Through use of silicon as the main material, superiorrotational characteristics can be achieved and superior durability canbe achieved. Moreover, fine processing (manufacturing) can be performed,and the actuator 1 can be downsized.

As for the substrate 2, the movable plate 221, the second axial members222 and 223, the driving member 211, the first axial members 212 and213, and the supporting section 23 can be formed from a substrate havinga layered structure, such as a silicon-on-insulator (SOI) substrate. Inthis case, the movable plate 221, the second axial members 222 and 223,the driving member 211, the first axial members 212 and 213, and thesupporting section 23 are preferably integrally formed from one layer ofthe layered-structure substrate.

As shown in FIG. 2, the substrate 2 is joined with the supportingsubstrate 3, with the bonding layer 4 therebetween. The supportingsubstrate 3 is formed, for example, with glass or silicon as the mainmaterial. The supporting substrate 3 has almost the same shape as thesupporting section 23 (in other words, has a frame-shape) in plan viewof the movable plate 221. However, the shape of the supporting substrate3 is not particularly limited as long as the supporting substrate 3 cansupport the substrate 2. The supporting substrate 3 can also be omitteddepending on the shape of the supporting section 23 and the like.

The bonding layer 4 formed between the supporting substrate 3 and thesubstrate 2 can be formed, for example, with glass, silicon, or SiO₂ asthe main material. However, the bonding layer 4 can be omitted. In otherwords, the substrate 2 and the supporting substrate 3 can be directlybonded.

As shown in FIG. 2, the counter substrate 5 is provided so as to facethe substrate 2, with the supporting substrate 3 therebetween. Thecounter substrate 5 is formed, for example, with glass or silicon as themain material.

A coil 62 is provided on the top surface of the counter substrate 5 togenerate a magnetic field acting on the permanent magnet 61. As shown inFIG. 2, the coil 62 is electrically connected with a voltage applyingunit 63. The permanent magnet 61, the coil 62, and the voltage applyingunit 63 form the driving unit 6.

As shown in FIG. 2, the permanent magnet 61 is longitudinally shaped.The permanent magnet 61 is joined with the bottom surface of the drivingmember 211, with adhesive layers 81 and 82 therebetween. In other words,the permanent magnet 61 is provided to a side adjacent to one side,opposing the other side on which the light reflecting section 221 a isdisposed, of the movable plate 221. This structure can prevent a lightscanning on the light reflector 221 a from being hindered by thepermanent magnet 61.

In plan view of FIG. 1, the permanent magnet 61 is provided along a linesegment (the line segment is also referred to, hereinafter, as a “linesegment J”) that passes through the intersection (also referred to,hereinafter, as an “intersection G”) of the rotation center axis X andthe rotation center axis Y, and slants with respect to each of therotation center axis X and the rotation center axis Y.

The permanent magnet 61 has an S pole at one end part while a north poleat the other part, in the longitudinal direction with respect to theintersection G. In other words, a line segment connecting the S pole andthe N pole of the permanent magnet 61 (in other words, the line segmentJ) is slanted with respect to each of the rotation center axis X and therotation center axis Y. The permanent magnet 61 is illustrated so as tohave the S pole at the left side while the N pole at the right side inits longitudinal direction in FIG. 2 for expository convenience.

In planar view of FIG. 1, a tilt angle θ of the line segment J withrespect to the rotation center axis X is preferably from 30 to 60degrees, more preferably from 40 to 50 degrees, and further preferablyalmost 45 degrees. As a result of the permanent magnet 61 being providedas described above, the movable plate 221 can be very smoothly rotatedaround each of the rotation center axis X and the rotation center axisY. On the other hand, when the tilt angle θ is less than the minimumvalue, the movable plate 221 cannot be smoothly rotated around the axisX depending on the strength of the voltage applied to the coil 62 andthe like. On the other hand, when the tilt angle θ exceeds the maximumvalue, the movable plate 221 cannot be smoothly rotated around the axisY depending on the strength of the voltage applied to the coil 62 andthe like.

According to the embodiment, the line segment J is slanted at 45 degreeswith respect to each of the rotation center axis X and the rotationcenter axis Y.

As shown in FIG. 2, a recess 611 is formed to a surface, at a sideadjacent to the movable plate 221, of the permanent magnet 61 (in otherwords, the top surface). The recess 611 is a relief section provided toavoid making contact between the permanent magnet 62 and the movableplate 221. As a result of the recess (relief section) 611 being formed,the rotation of the movable plate 221 around the rotation center axis Ycan be performed smoothly. In addition, because the relief section isthe recess 611, the contact between the permanent magnet 61 and themovable plate 221 can be very easily prevented. However, the reliefsection is not particularly limited, as long as the contact between themovable plate 221 and the permanent magnet 61 can be prevented. Forexample, the relief section can be a through-hole formed in a directionperpendicular to each of the rotation center axis X and the rotationcenter axis Y. For example, when the adhesive layers 81 and 82 are thickenough to prevent the contact between the movable plate 221 and thepermanent magnet 61 or the like, the recess 611 can be omitted.

The permanent magnet 61 is not particularly limited. For example, amagnetized hard magnetic material such as a neodymium magnet, a ferritemagnet, a samarium-cobalt magnet, an alnico magnet, and a bond magnetcan be preferably used.

The permanent magnet 61 can be configured by a magnetized hard magneticmaterial (in other words, a permanent magnet) being provided on thebottom surface of the driving member 211. Alternatively, the permanentmagnet 61 can be configured by the hard magnetic material being providedon the driving member 211 and then magnetized.

The adhesive layers 81 and 82 provided to join the permanent magnet 61and the driving member 211 are formed, for example, with an adhesive. Asa result, the driving member 211 and the permanent magnet 61 can befirmly adhesively bonded. However, the material of the adhesive layers81 and 82 are not particularly limited as long as the permanent magnet61 can be provided on the bottom surface of the driving member 211. Theadhesive layers 81 and 82 can be omitted depending on the bonding methodof the permanent magnet 61 and the driving member 211.

The coil 62 is provided directly below the permanent magnet 61. In otherwords, the coil 62 is provided so as to face the respective bottomsurfaces of the movable plate 221 and the driving member 211. As aresult of the coil 62 being provided directly below the permanent magnet62 in this way, the magnetic field generated by the coil 62 canefficiently work on the permanent magnet 62. As a result, powerconsumption reduction and size reduction of the actuator 1 can beachieved.

As shown in FIG. 1, the coil 62 is formed so as to surround an outercircumference of the driving member 211, in plan view of FIG. 1. As aresult of the coil 62 being formed in this way, contact between thedriving member 211 and the coil 62, when the actuator 1 is driven, canbe reliably prevented. Therefore, a separating distance between the coil62 and the permanent magnet 61 can be shortened greatly. The magneticfield generated by the coil 62 can efficiently work on the permanentmagnet 61. In other words, the power consumption reduction and sizereduction of the actuator 1 can be achieved. The coil 62 can be windedaround a magnetic core.

The coil 62 is electrically connected to the voltage applying unit 63.As a result of the voltage applying unit 63 applying the voltage to thecoil 62, the coil 62 generates a magnetic field having magnetic flux inan axial direction perpendicular to each of the rotation center axis Xand the rotation center axis Y.

As shown in FIG. 3, the voltage applying unit 63 includes a firstvoltage generating section 631, a second voltage generating section 632,and a voltage superimposing section 633. The first voltage generatingsection 631 generates a first voltage V1 to rotate the movable plate 221around the rotation center axis X. The second voltage generating section632 generates a second voltage V2 to rate the movable plate 221 aroundthe rotation center axis Y. The voltage superimposing section 633superimposes the first voltage V1 and the second voltage V2 and appliesthe superimposed voltage to the coil 62.

As shown in FIG. 4A, the first voltage generating section 631 generatesthe first voltage V1 that periodically changes at a period T1 (voltagefor vertical scanning).

The first voltage V1 has a waveform that is like a sawtooth. Therefore,the actuator 1 can effectively vertically scan light (sub-scan). Thewaveform of the first voltage V1 is not limited thereto. A frequency(1/T1) of the first voltage V1 is not limited as long as the frequencyis suitable for vertical scanning. However, the voltage is preferablyfrom 30 to 80 Hz (about 60 Hz).

According to the embodiment, the frequency of the first voltage V1 isadjusted to be different from a torsional resonance frequency of thefirst oscillatory system 21 composed of the driving member 211 and thepair of first axial members 212 and 213.

On the other hand, the second voltage generating section 632 generatesthe second voltage V2 (voltage for horizontal scanning) thatperiodically changes at a period T2 differing from the period T1.

The second voltage V2 has a waveform that is like a sinewave. Therefore,the actuator 1 can effectively main-scan light. The waveform of thesecond voltage V2 is not limited thereto.

The frequency of the second voltage V2 is preferably higher than thefrequency of the first voltage V1. In other words, the period T2 ispreferably shorter than the period T1. As a result, the movable plate221 can be more reliably and smoothly rotated around the rotation centeraxis X at the frequency of the first voltage V1 and rotated around therotation center axis Y at the frequency of the second voltage V2.

The frequency of the second voltage V2 is not particularly limited aslong as the frequency differs from the frequency of the first voltage V1and is a frequency suitable for horizontal scanning. However, thefrequency is preferably from 10 to 40 kHz. In this way, as a result ofthe frequency of the second voltage V2 being from 10 to 40 kHz and thefrequency of the first voltage V1 being about 60 Hz as described above,the movable plate 221 can be rotated around the respective axes of therotation center axis X and the rotation center axis Y at a frequencysuitable for drawing an image on a display. However, the frequency ofthe first voltage V1, the frequency of the second voltage V2, thecombination of the frequency of the first voltage V1 and the frequencyof the second voltage V2, and the like are not particularly limited, aslong as the movable plate 221 can rotate around each of the rotationcenter axis X and the rotation center axis Y.

According to the embodiment, the frequency of the second voltage V2 isadjusted to be equal with a torsional resonance frequency of the secondoscillatory system 22 composed of the movable plate 221 and the pair ofsecond axial members 222 and 223. In other words, the second oscillatorysystem 22 is designed (manufactured) such that the torsional resonancefrequency is a frequency suitable for horizontal scanning. Therefore, arevolution angle of the movable plate 221 around the rotation centeraxis Y can be made larger.

When the resonance frequency of the first oscillatory system 21 isf₁[Hz] and the resonance frequency of the second oscillatory system 22is f₂[Hz], f₁ and f₂ preferably satisfy a relationship of f₁>f₂, andmore preferably a relationship of f₂≧10f₁. As a result, the movableplate 221 can more smoothly rotate around the rotation center axis X atthe frequency of the first voltage V1 and rotate around the rotationcenter axis Y at the frequency of the second voltage V2.

The first voltage generating section 631 and the second voltagegenerating section 632 are respectively connected to the controllingsection 7 and are driven based on a signal from the controlling section7. The voltage superimposing section 633 is connected to the firstvoltage generating section 631 and the second voltage generating section632.

The voltage superimposing section 633 includes an adder 633 a forapplying a voltage to the coil 62. The adder 633 a receives the firstvoltage V1 from the first voltage generating section 631 and the secondvoltage V2 from the second voltage generating section 632. The adder 633a superimposes the voltages and applies the superimposed voltage to thecoil 62.

The actuator 1 configured as described above is driven as follows.According to the embodiment, as described above, the frequency of thefirst voltage V1 is set to a value different from the torsionalresonance frequency of the first oscillatory system 21. The frequency ofthe second voltage V2 is set to be equal to the torsional resonancefrequency of the second oscillatory system 22 and greater than thefrequency of the first voltage V1 (for example, the frequency of thefirst voltage V1 is 60 Hz and the frequency of the second voltage V2 is15 kHz.)

For example, the voltage superimposing section 633 superimposes thefirst voltage V1 shown in FIG. 4A, and the second voltage V2 shown inFIG. 4B, and applies the superimposed voltage to the coil 62.

Then, a magnetic field (referred to as a “magnetic field A1”) that tendsto attract the vicinity of the adhesive layer 81 of the driving member211 towards the coil 62 and repel the vicinity of the adhesive layer 82of the driving member 211 from the coil 62, and a magnetic field(referred to as a “magnetic field A2”) that tends to repel the vicinityof the adhesive layer 81 of the driving member 211 from the coil 62 andattract the vicinity of the adhesive layer 82 of the driving member 211towards the coil 62 are alternately switched by the first voltage V1.

Here, in plan view of FIG. 1, the adhesive layer 81 is positioned on oneside of the driving member 211 relative to the rotation center axis X.The adhesive layer 82 is positioned on the other side. In other words,the pair of first adhesive layers 81 and 82 is provided on the drivingmember 211 so as to sandwich the rotation center axis X, in plan view ofFIG. 1. Therefore, as a result of the magnetic field A1 and the magneticfield A2 being alternately switched, the driving member 211 rotatesaround the rotation center X at the frequency of the first voltage V1with the movable plate 221, while the first axial members 212 and 213are twisted and deformed.

The frequency of the first voltage V1 is set to be significantly lowerthan the frequency of the second voltage V2. The resonance frequency ofthe first oscillatory system 21 is designed to be lower than theresonance frequency of the second oscillatory system 22 (for example,1/10 or less than the resonance frequency of the second oscillatorysystem 22). In other words, the driving member 211 rotates around therotation center axis X by the first voltage V1 because the firstoscillatory system 21 is designed to more easily oscillate compared tothe second oscillatory system 22. In other words, the driving member 211is prevented from rotating around the rotation center axis X by thesecond voltage V2.

On the other hand, a magnetic field (referred to as a “magnetic fieldB1”) that tends to attract the vicinity of the adhesive layer 81 of thedriving member 211 towards the coil 62 and repel the vicinity of theadhesive layer 82 of the driving member 211 from the coil 62, and amagnetic field (referred to as a “magnetic field B2”) that tends torepel the vicinity of the adhesive layer 81 of the driving member 211from the coil 62 and attract the vicinity of the adhesive layer 82 ofthe driving member 211 towards the coil 62 are alternately switched bythe second voltage V2.

Here, in plan view of FIG. 1, the adhesive layer 81 is positioned on oneside of the driving member 211 relative to the rotation center axis Y.The adhesive layer 82 is positioned on the other side. In other words,the pair of first adhesive layers 81 and 82 is provided on the drivingmember 211 so as to sandwich the rotation center axis Y, in plan view ofFIG. 1. Therefore, as a result of the magnetic field B1 and the magneticfield B2 being alternately switched, the movable plate 221 rotatesaround the rotation center Y at the frequency of the second voltage V2(15 kHz), while the second axial members 222 and 223 are twisted anddeformed.

The frequency of the second voltage V2 is equal to the torsionalresonance frequency of the second oscillatory system 22. Therefore, themovable plate 221 can be dominantly rotated around the rotation centeraxis Y by the second voltage V2. In other words, the movable plate 221is prevented from rotating around the rotation center axis Y by thefirst voltage V1.

Therefore, in the actuator 1, as a result of the voltage obtained bysuperimposing the first voltage V1 and the second voltage V2 beingapplied to the coil 62, the movable plate 221 can be rotated around therotation center axis X at the frequency of the first voltage V1 androtated around the rotation center axis Y at the frequency of the secondvoltage V2. As a result, the movable plate 221 can be very smoothlyrotated around each of the rotation center axis X and the rotationcenter axis Y while achieving low costs and downsizing.

In particular, because the respective numbers of permanent magnets andcoils serving as a drive source can be reduced, a simple and compactconfiguration can be achieved.

As a result of the first voltage V1 and the second voltage V2 beingchanged accordingly, a desired oscillation characteristic can beobtained without changes being made to the designs of the substrate 2and the permanent magnet 61.

In the actuator 1, the permanent magnet 61 is provided on the drivingmember 211, and the coil 62 is provided on the counter substrate 5 so asto face the permanent magnet 61. In other words, the coil 62 serving asa heating element is not provided in the first oscillatory system 21.Therefore, thermal expansion of the substrate 2 caused by the heatgenerated from the coil 62 through energization can be suppressed. As aresult, the actuator 1 can achieve the desired oscillationcharacteristics even when consecutively used over a long period of time.

The actuator 1 includes the light reflecting section 221 a. Therefore,the actuator 1 can be suitably applied to, for example, an opticalscanner included in image forming devices, such as laser printers, barcode readers, confocal scanning laser microscopes, and imaging displays.The optical scanner of the present invention has the same configurationas the above-described actuator. Explanation thereof will be omitted.

Here, based on FIG. 5, when the actuator 1 is used as the opticalscanner in the imaging display will be described as an example of theimage forming device. A longitudinal direction of a screen S is referredto as a “horizontal direction”. A direction perpendicular to thelongitudinal direction is referred to as a “vertical direction”. Therotation center axis X is in parallel with the horizontal direction ofthe screen S. The rotation center axis Y is in parallel with thevertical direction of the screen S.

An image forming device (projector) 9 includes a light source device 91,a plurality of dichroic mirrors 92, and the actuator 1. The light sourcedevice 91 emits light, such as a laser.

The light source device 91 includes a red light source device 911 thatemits a red light component, a blue light source device 912 that emits ablue light component, and a green light source device 913 that emits agreen light component.

Each dichroic mirror 92 is an optical element that synthesizes the lightcomponents respectively emitted from the red light source device 911,the blue light source device 912, and the green light source device 913.

The projector 9 is configured such that, based on image information froma host computer (not shown), the dichroic mirrors 92 synthesizes thelight components emitted from the light source device 91 (the red lightsource device 911, the blue light source device 912, and the green lightsource device 913). The actuator 1 two-dimensionally scans thesynthesized light, and a color image is formed on the screen S.

During the two-dimensional scan, the light reflected by the lightreflecting section 221 a is scanned (main scan) in the horizontaldirection of the screen S, as a result of the movable plate 221 of theactuator 1 rotating around the rotation center axis Y. On the otherhand, the light reflected by the light reflecting section 221 a isscanned (sub-scan) in the vertical direction of the screen S by themovable plate 221 of the actuator 1 rotating around the rotation centeraxis X.

In FIG. 5, after the actuator 12 two-dimensionally scans the lightsynthesized by the dichroic mirrors 92, the image is formed on thescreen S after the light is reflected by a fixed mirror M. However, thefixed mirror M can be omitted. The light two-dimensionally scanned bythe actuator 1 can be directly irradiated onto the screen S.

While the actuator, the optical scanner, and the image forming apparatusof the invention are described based on the illustrated embodiments thusfar, but the invention is not limited to those embodiments. For example,the actuator, the optical scanner, and the image forming apparatus ofthe invention may include any substitute that has the same function asits original structure and may include any additional structure.

According to the above-described embodiment, the actuator is almostsymmetrical relative to each of the X-axis and the Y-axis. However, theactuator can be asymmetrical.

According to the above-described embodiment, that using a permanentmagnet having a longitudinal shape is described. However, the shape ofthe permanent magnet is not particularly limited, as long as the linesegment connecting both poles is provided so as to slant with respect toeach of the X-axis and the Y-axis, in a plan view of the movable plate.For example, the permanent magnet can have a circular or square shape,in the plan view of the movable plate. In addition, for example, a pairof yokes can be provided so as to sandwich the permanent magnet in adirection of the line segment connecting both poles. The yokes can leadthe magnetic flux.

1. An actuator, comprising: a first oscillatory system including aframe-shaped driving member and a pair of first axial members holdingthe driving member from both ends so as to allow the driving member torotate around an X-axis; a second oscillatory system including a movableplate provided inside the driving member and a pair of second axialmembers holding the movable plate to the driving member from both endsso as to allow the movable plate to rotate around a Y-axis perpendicularto the X axis; and a driving unit including a permanent magnet providedon the driving member, a coil provided so as to face the permanentmagnet, and a voltage applying unit applying a voltage to the coil,wherein, the permanent magnet is provided such that a line segmentconnecting both poles is slanted with respect to each of the X-axis andthe Y-axis, in a plan view of the movable plate, and the voltageapplying unit includes a voltage generating section that generates afirst alternating voltage and a second alternating voltage each of whichhaving a frequency different from each other, and a voltagesuperimposing section that superimposes the first voltage and the secondvoltage, and the movable plate is rotated around the Y-axis at afrequency of the second voltage while being rotated around the X axis ata frequency of the first voltage by applying the voltage superimposed bythe voltage superimposing section to the coil.
 2. The actuator accordingto claim 1, wherein the frequency of the first voltage is equal to aresonance frequency of the first oscillatory system or the frequency ofthe second voltage is equal to a resonance frequency of the secondoscillatory system.
 3. The actuator according to claim 2, wherein thefrequency of the second voltage is equal to the resonance frequency ofthe second oscillatory system and the frequency of the first voltagediffers from the resonance frequency of the first oscillatory system. 4.The actuator according to claim 1, wherein the frequency of the secondvoltage is higher than the frequency of the first voltage.
 5. Theactuator according to claim 1, wherein the permanent magnet has alongitudinal shape and is provided along a line segment that passesthrough an intersection of the X-axis and the Y-axis, and slants at anangle of from 30 to 60 degrees with respect to the X-axis or the Y-axis.6. The actuator according to claim 1, wherein the permanent magnet has arelief section to avoid making contact with the movable plate.
 7. Theactuator according to claim 6, wherein the relief section is a recessformed to a surface of the permanent magnet, the surface being at a sideadjacent to the movable plate.
 8. The actuator according to claim 1,wherein the coil is provided directly below the permanent magnet.
 9. Theactuator according to claim 1, wherein the coil is formed so as tosurround an outer circumference of the driving member, in the plan viewof the movable plate.
 10. The actuator according to claim 1, wherein themovable plate has a light reflecting section having a light reflectivecharacteristic on one surface opposing the other surface facing thepermanent magnet.
 11. An optical scanner, comprising: a firstoscillatory system including a frame-shaped driving member and a pair offirst axial members holding the driving member from both ends so as toallow the driving member to rotate around an X-axis; a secondoscillatory system including a movable plate that is provided inside thedriving member and has a light reflecting section having a lightreflective characteristic, and a pair of second axial members holdingthe movable plate to the driving member from both ends so as to allowthe movable plate to rotate around a Y-axis perpendicular to the X-axis;and a driving unit including a permanent magnet provided on the drivingmember, a coil provided so as to face the permanent magnet, and avoltage applying unit applying a voltage to the coil, wherein, thepermanent magnet is provided such that a line segment connecting bothpoles is slanted with respect to each of the X-axis and the Y-axis, in aplan view of the movable plate, and the voltage applying unit includes avoltage generating section that generates a first alternating voltageand a second alternating voltage each of which has a frequency differentfrom each other, and a voltage superimposing section that superimposesthe first voltage and the second voltage, and the movable plate isrotated around the Y-axis at a frequency of the second voltage whilebeing rotated around the X-axis at a frequency of the first voltage byapplying the voltage superimposed by the voltage superimposing sectionto the coil, and light reflected by the light reflecting section istwo-dimensionally scanned.
 12. An image forming device, comprising anoptical scanner including: a first oscillatory system including aframe-shaped driving member and a pair of first axial members holdingthe driving member from both ends so as to allow the driving member torotate around an X-axis, a second oscillatory system including a movableplate that is provided inside the driving member and has a lightreflecting section having a light reflective characteristic, and a pairof second axial members holding the movable plate to the driving memberfrom both ends so as to allow the movable plate to rotate around aY-axis perpendicular to the X-axis, and a driving unit including apermanent magnet provided on the driving member, a coil provided so asto face the permanent magnet, and a voltage applying unit applying avoltage to the coil, wherein, the permanent magnet is provided such thata line segment connecting both poles is slanted with respect to each ofthe X-axis and the Y-axis, in a planar view of the movable plate, andthe voltage applying unit includes a voltage generating section thatgenerates a first alternating voltage and a second alternating voltageeach of which has a frequency different from each other, and a voltagesuperimposing section that superimposes the first voltage and the secondvoltage, and the movable plate is rotated around the Y-axis at afrequency of the second voltage while being rotated around the X-axis ata frequency of the first voltage by applying the voltage superimposed bythe voltage superimposing section to the coil, and light reflected bythe light reflecting section is two-dimensionally scanned.